asarandi / game-achievements-system Goto Github PK

this is my solution to a coding challenge i received when i applied for a backend engineer position.

the project can be summarized as "an achievements system for a fictional online game". please see SPEC.md for challenge details.

i decided to implement a restful api in go, so this is a web server connected to a database that exposes several endpoints which accept GET, POST, PUT and DELETE requests in order to create, read, update and delete records

project components:

• server: https://golang.org/pkg/net/http/
• router: https://github.com/gorilla/mux
• database: https://github.com/jinzhu/gorm

• individual functions that are run at the end of each game to check if a player qualifies for an achievement

• program configuration settings: server listening address, database file name, etc

• contains game related logic: adding teams to games, setting winners at the end of a game, etc

• functions responsible for each endpoint and request type

• initializes other program components and launches server

• unit tests and sample data driver

• data structures and generalized functions for manipulating database records

• errors and json response encoding

• endpoints, http request methods

before running the program, make sure to install the dependencies, this only has to be done once:

go get github.com/gorilla/mux

go get github.com/jinzhu/gorm

go get github.com/jinzhu/gorm/dialects/sqlite

to build and run:

go build && ./game-achievements-system

or just run without building:

go run .

program should print server ready at: 0.0.0.0:4242

file main_test.go contains unit tests and also acts as a driver.

the test scenario is simple:

• create the four default achievements
• create 10 sample members (players)
• create 4 sample teams
• start 2 games
• update member stats
• close games
• verify that server awarded correct wins and achievements to qualifying members

to run the tests:

go test -v

the test will fail if the database file is already populated with data, if that happens just remove database.sqlite and re-run the test - or - you could edit config.go and set databaseFile = ":memory:"

to address SPEC.md requirement #7, "add a new statistic and create a new achievement ..":

to add a simple statistic like "number of collected coins" during a game we would simply add it to our Stat object which is defined in models.go; it might look like this:

type Stat struct {
	gorm.Model
	GameID       uint `json:"game_id"`
	TeamID       uint `json:"team_id"`
	MemberID     uint `json:"member_id"`
	NumAttacks   uint `json:"num_attacks"`
	NumHits      uint `json:"num_hits"`
	AmountDamage uint `json:"amount_damage"`
	NumKills     uint `json:"num_kills"`
	InstantKills uint `json:"instant_kills"`
	NumAssists   uint `json:"num_assists"`
	NumSpells    uint `json:"num_spells"`
	SpellsDamage uint `json:"spells_damage"`
	NumCoins     uint `json:"num_coins"`		// <<--- we added a new statistic
	IsWinner     bool `json:"is_winner"`
}

next, we want to add the achievement to the database; here is one way of doing that:

curl -X POST 0.0.0.0:4242/achievements --data '{"name": "1UP", "slug": "oneup", "desc": "You have collected 100 or more coins during a single game! Wow!", "img": "https://www.pngfind.com/pngs/m/22-226955_mario-mushroom-png-mario-1-up-mushroom-transparent.png"}'

if successful, the server replies "success":true, "code":201

{"success":true,"code":201,"message":"ok","result":{"ID":5,"CreatedAt":"2019-08-09T23:44:41.040203-07:00","UpdatedAt":"2019-08-09T23:44:41.040203-07:00","DeletedAt":null,"slug":"oneup","name":"1UP","desc":"You have collected 100 or more coins during a single game! Wow!","img":"https://www.pngfind.com/pngs/m/22-226955_mario-mushroom-png-mario-1-up-mushroom-transparent.png"}}

then, in achievements.go we want to add a function which will check if a member qualifies for the achievement; function signature should be func (Stat) bool it might look like this:

func isOneUpAward(stat Stat) bool {
	if stat.NumCoins >= 100 {
		return true
	}
	return false
}

we also have to "register" the achievement by adding it to the asf list which is in achievements.go;

    asf = []typeAsf{
		{achievement: Achievement{}, slug: "sharpshooter", function: isSharpshooterAward},
		{achievement: Achievement{}, slug: "bruiser", function: isBruiserAward},
		{achievement: Achievement{}, slug: "veteran", function: isVeteranAward},
		{achievement: Achievement{}, slug: "bigwinner", function: isBigwinnerAward},
		{achievement: Achievement{}, slug: "oneup", function: isOneUpAward},		// <<--- 1UP new achievement
	}

it is important that the slug field matches the slug that we previously inserted into database.

last step is to restart the server. at the end of each game the new achievement will be awarded to qualifying members.

we can create more interesting achievements by using sql capabilities of the database,

for example to check if a member qualifies for a "Win-Five-Games-In-A-Row" achievement:

func isWonLastFive(stat Stat) bool {
	lastFiveStats := []Stat{}
	db.Order("CreatedAt desc").Limit(5).Joins("JOIN games ON games.id = stats.game_id AND games.status = ? AND stats.member_id = ?", finishedGame, stat.MemberID).Find(&lastFiveStats)
	if len(lastFiveStats) == 5 {
		result := true
		for i := range lastFiveStats { result = result && lastFiveStats[i].IsWinner }
		return result
	}
	return false;
}

• https://en.wikipedia.org/wiki/Create,_read,_update_and_delete
• https://en.wikipedia.org/wiki/Representational_state_transfer
• https://medium.com/studioarmix/learn-restful-api-design-ideals-c5ec915a430f
• http://www.golangprograms.com/golang-restful-api-using-grom-and-gorilla-mux.html
• http://jinzhu.me/gorm/crud.html
• https://pragmacoders.com/blog/building-a-json-api-in-go
• https://medium.com/@adigunhammedolalekan/build-and-deploy-a-secure-rest-api-with-go-postgresql-jwt-and-gorm-6fadf3da505b
• https://medium.com/@shazow/how-i-design-json-api-responses-71900f00f2db
• https://github.com/mousey/fifa-soccer-12-ultimate-team-data